Coated Electric Wire

ABSTRACT

A halogen-free light-weighted coated electric wire has a conductor and a coating layer covering the outer circumference of the conductor. The coating layer includes an outer layer having a halogen-free resin composition and Shore D hardness of 50 or above and an inner layer having an olefin based flame retardant composition. A total thickness of the coating layer is 0.3 mm or less

TECHNICAL FIELD

The present invention relates to halogen free coated electric wireswhich are used for parts of automobiles or the like and do not containhalogen elements.

BACKGROUND ART

Polyvinylchloride resins, having excellent flame retardance, have beengenerally used as a coating material for coated electric wires employedto parts of automobiles, electric and electronic devices, and the like.

However, the polyvinylchloride resins, contrary to their excellent flameretardance, have a problem that, since they contain halogen elements intheir molecular chains, they release harmful halogenous gases toatmosphere while the automobiles are fired or the electric andelectronic devices are burned for disposal, causing environmentalpollution.

To solve this problem, flame-retardant resin compositions freed fromhalogens are developed which comprise polyethylene or polypropylene as abase resin and a metal hydrate such as magnesium hydroxide as a flameretardant. These flame-retardant halogen-free resin compositions,however, have a disadvantage of poor mechanical properties such asabrasion resistance, since they require addition of metal hydrates in alarge amount as the flame retardant.

To solve such disadvantage mentioned above, a coated electric wirehaving two coating layers has been developed (Patent Document 1).

The coating layers of the coated electric wire are composed of an outerlayer and inner layer with blending a flame retardant in the inner layerin larger amount than in the outer layer, thereby preventing the outerlayer from deterioration of mechanical properties as well as retainingmore flame retardancy in the inner layer.

However, if the coated electric wire relies only on an inner layer aboutits flame retardancy, a large amount of flame retardant needs to beadded, and the inner layer drastically loses the flexibility thereof,deteriorating fundamental properties required to the electric wire.Therefore, two-layer coated electric wires conventionally providedcannot avoid to add a certain amount of a flame retardant in the outerlayer thereof. Other additives, such as antiaging agents, are also addedto the outer layer for various purposes. However, such additives areadded in so large amount that resulting mechanical properties such asabrasion resistance and scratch damage resistance are not necessarilysatisfactory.

Moreover, requirements of weight saving for various coated electricwires currently have become stronger. Particularly, according torequirements of lightening a body of automobiles, the requirements ofsaving weights of coated electric wires spread not only to reducingdiameter of conductors but also to thinning coating layers. As theresult, scratch damage resistance of the coated electric wires hasbecome a big issue. In other words, when thick coating layers areallowed, the problems of scratch damage don't appear, but when thethickness of the coating layers becomes smaller, conductors could beexposed by even a slight scratch damage.

Furthermore, as wiring becomes more complex, flexibility of coatedelectric wires becomes more important, causing difficulty to add flameretardants to the inner layer in a large amount.

Patent Document: JP 1-302611A.

DISCLOSURE OF THE INVENTION Problems to Be Solved by the Invention

The invention is to provide a halogen-free and lightweight coatedelectric wire which has excellent flame retardance as well as superiormechanical properties, particularly in scratch damage resistance, andmoreover has a flexibility allowing more complex wiring.

Means to Solve the Problems

The inventors, after having intensively studied, have found thefollowings, and then completed the invention:

an electric wire coated with a coating layer having a certain thicknessor less can endure scratch damages by providing a Shore D hardness of 50or more to the outer layer thereof;

to achieve this endurance, an additive to be added to the outer layermust be suppressed in a small amount;

this suppression increases an amount of a flame retardant to be added toan inner layer and causes decrease of flexibility thereof;

this flexibility decrease however hardly affects to a whole flexibilityof the electric wire having the coating layer having a certain thicknessor less because the whole thickness of the layers is thin; and

consequently such coated electric wire can secure a flexibilitysufficiently allowing more complex wiring.

One of the preferable aspects of the present invention is a coatedelectric wire having a conductor and a coating layer covering the outercircumference of the conductor.

The coating layer has an outer layer having a halogen-free resincomposition with a Shore D hardness of 50 or more and an inner layerhaving an olefin based flame retardant resin composition.

The coating layer has a total thickness of 0.3 mm or less.

Because the outer layer is a layer having a Shore D hardness of 50 ormore, the conductor is not exposed under usual scratch damages even ifthe total thickness of the coating layer is small.

Because the inner layer is composed of a layer having an olefin basedflame retardant resin composition, the flame retardance can be securedby this layer. On the other hand, the outer layer must suppress additionof various additives in small amounts to secure a Shore D hardness of 50or more. Because of this suppression, an increased amount of flameretardant need be added in the inner layer. However this increasedaddition of the flame retardant has little affect to a flexibility ofthe electric wire because of a thin coating layer having a total coatinglayer thickness of 0.3 mm or less, thereby retaining a flexibility ofthe electric wire to allow more complex wiring. If the total thicknessof the coating layer is less than 0.1 mm, it causes difficulty to endurescratching damages, thus the total thickness is preferably 0.1 mm ormore.

Because an olefin resin composition not containing halogens in itsmolecular chain is used for the inner layer and a halogen-free resincomposition not containing halogens is also used for the outer layer,the coated electric wire does not cause a problem of environmentalpollution. Therefore, the coated electric wire is particularlypreferably used as electric wires for automobiles.

An intermediate layer having a halogen-free resin composition may bedisposed between the outer layer and inner layer.

An intermediate layer comprising a halogen-free resin composition may bedisposed between the outer layer.

The halogen-free resin composition used for the outer layer ispreferably an olefin resin composition due to its character of repellingwater and inexpensive cost.

One of the preferable aspects of the present invention is the abovecoated wire, wherein the halogen-free resin composition is an olefinresin composition.

The outer layer is preferably added with additives, particularly oxidefillers, silicate fillers, antiaging agents, lubricants, plasticizers,or antistatic agents, to enhance various properties thereof, theadditives. In this case, if the additives are added more than 30 partsby weight with respect to 100 parts by weight of a base polymer of theouter layer mentioned above, the outer layer becomes difficult toachieve the Shore D hardness of 50 or more. Therefore, the amount of theadditives is preferably suppressed to 30 parts by weight or less.

One of the preferable aspects of the present invention is the abovecoated wire, wherein the halogen-free resin composition is an olefinresin composition.

One of the preferable aspects of the present invention is the abovecoated wire, wherein the outer layer contains oxide fillers, silicatefillers, antiaging agents, lubricants, plasticizers, or antistaticagents in an amount of 30 parts by weight or less with respect to 100parts by weight of the base polymer of the outer layer mentioned above.

If a layer thickness of the outer layer is less than 1 μm, possibilitiesof exposing the conductor increase depending on situations of damagesscratched. Therefore, the layer thickness of the outer layer ispreferably 1 μm or more. On the other hand, if the layer thicknessthereof is more than 100 μm, it tends to become difficult to secure aflame retardance of the whole wire with a flame retardant added to theinner layer. Therefore, the layer thickness of the outer layer ispreferably 1 to 100 μm, more preferably 5 to 100 μm. The optimal layerthickness is 20 to 60 μm.

One of the preferable aspects of the present invention is the abovecoated wire, wherein the layer thickness of the outer layer is 1 to 100μm.

The flame-retardant olefin resin composition for the inner layer can beobtained by providing flame retardancy to an olefin resin compositionwith a flame retardant or the like. For this purpose, preferably, ametal hydrate is used as the flame retardant. The metal hydrates canexert the flame retardance to the whole coated electric wire when it isprovided to the inner layer in an amount of 50 parts by weight or morewith respect to 100 parts by weight of the base polymer. On the otherhand, it tends to reduce mechanical properties such as flexibility whenbeing provided in an amount of more than 200 parts by weight, thereforepreferably being 200 parts by weight or less.

One of the preferable aspect of the present invention is the abovecoated electric wire, wherein the inner layer contains a metal hydratein an amount of 50 to 200 parts by weight with respect to 100 parts byweight of a base polymer of the inner layer.

As the layer thickness of the outer layer increases, the metal hydrateadded as a flame retardant in the inner layer must be increased.According to results a study conducted by the inventors about relationsbetween the layer thickness of the outer layer and the amount of a flameretardant within the range of amount defined above with using variouskinds of metal hydrates, when letting X (μm) be the layer thickness ofthe outer layer and Y(phr) be the amount of a flame retardant to beadded to the inner layer, particularly preferable flame retardance canbe achieved by satisfying the relation represented by the formulaY−40≧1.2X.

One of the preferable aspects of the present invention is the abovecoated electric wire, wherein, when letting X (μm) be the layerthickness of the outer layer and Y(phr) be the amount of a flameretardant to be added to the inner layer, the formula Y−40≧1.2X issatisfied.

The coating layers increase their heat resistance by being cross-linked.Since the coated electric wire has a small total thickness of thecoating layers, it is significant to cross link the above-mentionedouter layer and/or inner layer depending on requirements.

One of the preferable aspects of the present invention is the abovecoated electric wire, wherein the outer layer and/or inner layer arecross linked.

Effects of the Invention

The coated electric wire of the invention can avoid a problem ofenvironmental pollution caused by halogenous gases, enables weightsaving of wires as well as never exposes conductors by scratching inspite of a small layer thickness of the coating layers thereof.Furthermore, it has flexibility sufficiently allowing more complexwiring with retaining the flame retardance.

BEST MODE FOR CARRYING OUT THE INVENTION

The coated electric wire of the invention has a conductor and a coatinglayer covering the outer circumference of the conductor, wherein thecoating layer includes an outer layer containing a halogen-free resincomposition with a Shore D hardness of 50 or more and an inner layercontaining an olefin based flame retardant resin composition, and thecoating layer has a total thickness of 0.3 mm or less.

The olefin resin used for the outer layer or inner layer of the coatedelectric wire of the invention may be a single olefin resin, acombination of two or more kinds of olefin resins, or a combination ofan olefin resin as a major ingredient and one or two or more kinds ofrubbers. When being used in combination, the olefin resin and rubber tobe used in combination may be combined as a single form thereof or maybe combined after making a mixture having an olefin resin of a majoringredient.

The olefin resins used for the invention preferably includepolypropylene, low-density polyethylene, linear low-densitypolyethylene, high-density polyethylene, ethylene-α-olefin copolymer,ethylene-vinyl ester copolymers, ethylene-α,β-unsaturated carboxylicacid alkyl ester copolymers, and the like.

In this case, methods for producing the ethylene-α-olefin copolymermentioned above include moderate- or low-pressure polymerization methodswith using Ziegler catalysts or single-site catalysts, and other knownmethods. The ethylene-α-olefin copolymer includes copolymers of ethyleneand an α olefin with carbon numbers of 3 to 20 such as propylene,1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene,1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene,1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene,9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1tetradecene.

The vinyl ester monomer used for producing the above-mentionedethylene-vinyl ester copolymers includes vinyl propionate, vinylacetate, vinyl caproate, vinyl caprylate, vinyl laurylate, vinylstearate, vinyl trifluoroacetate, and the like.

The α,β-unsaturated carboxylic acid alkyl ester monomer used forproducing the ethylene-α,β-unsaturated carboxylic acid alkyl estercopolymers includes methyl acrylate, methyl metaacrylate, ethylacrylate, ethyl metaacrylate, and the like.

As mentioned above, the olefin resin used for the outer layer or innerlayer of the invention may be used in combination with a rubber. Therubbers preferably include ethylene-propylene-based rubbers,butadiene-based rubbers, isoprene-based rubbers, natural rubbers,nitrile rubbers, isobutylene rubbers, and the like.

In this case, the above mentioned ethylene-propylene-based rubbersinclude random copolymers mainly composed of ethylene and propylene,random copolymers mainly composed of ethylene, propylene and a dienemonomer, as the third component, such as dicyclopentadiene or ethylidenenorbornene, and the like.

The above mentioned butadiene-based rubbers are defined by copolymerscomprising butadiene as an ingredient, which include styrene-butadieneblock copolymers and hydrogenated or partially hydrogenated derivativesthereof such as styrene-ethylene-butadiene-styrene copolymers,1,2-polybutadiene, maleic anhydride-modifiedstyrene-ethylene-butadiene-styrene copolymers, modified butadienerubbers having a core-shell structure, and the like.

The above mentioned isoprene-based rubbers are defined by copolymerscomprising isoprene as an ingredient, which include styrene-isopreneblock copolymers and hydrogenated or partially hydrogenated derivativesthereof such as styrene-ethylene-isoprene-styrene copolymers, maleicanhydride-modified styrene-ethylene-isoprene-styrene copolymers,modified isoprene rubbers having a core-shell structure, and the like.

The flame-retardant olefin resin composition used for the inner layer ofthe invention is preferably an olefin resin composition added with ametal hydrate as a flame retardant.

The metal hydrate preferably includes magnesium hydroxide, aluminumhydroxide, or calcium hydroxide. Among them, magnesium hydroxide ispreferable because of its high decomposition temperature of about 360°C.

Their average particle diameter (D50) is preferably 0.5 to 5.0 μm. Whenthe average particle diameter (D50) is less than 0.5 μm, the particlesoften cause secondary agglomeration with each other, resulting inlowering of a mechanical strength. When the average particle diameter(D50) is more than 5.0 μm, a mechanical strength is also lowered and anappearance is often deteriorated.

When being used for various materials, the surface of metal hydrates isconventionally treated with various agents. In this invention, thesurface thereof may be treated with a suitable agent and by a suitablemethod depending on requirements to improve mechanical properties andthe like. The agents used for the surface treatment preferably includefatty acids, fatty acid metal salts, silane coupling agents, titanatecoupling agents, and the like.

When the coating layer of the coated electric wire of the invention iscross linked to improve heat resistance and the like, the cross-linkingmay be carried out by irradiating an ionizing radiation or using across-linking agent such as organic peroxides. When a coated electricwire with thin coating layer is cross linked, a cross-linking auxiliaryis preferably used for effectiveness.

Materials for the conductor of coated electric wire of the invention arenot particularly limited, preferably being copper, aluminum, and thelike. The conductor may be a single wire or a twisted wire. A twistedwire is preferable in view of flexibility. The conductor preferably hasa cross sectional area of 0.05 to 2.0 mm².

EXAMPLES

Examples and Comparative Examples are described as follows. Theinvention should not be construed to be limited thereto. Variousmodifications can be conducted to the following Examples within thescope identical or equivalent to the invention.

In Examples and Comparative Examples, electric wires were produced bypreparing a conductor with a cross sectional area of 0.5 mm² composed oftwisting seven soft-annealed copper wires, and then covering the outercircumference of the conductor by extrusion with an inner layer andouter layer, each of which consists of an insulating layer representedin the following Tables respectively and of which total thickness was0.20 mm. The electric wires thus produced were subjected to variousevaluations with the following evaluation methods.

(Evaluation of Abrasion Resistance)

According to the standard of JASO D611-94 defined by Society ofAutomotive Engineers of Japan, Inc., blade reciprocating method wasapplied as follows:

cutting out the test piece with 750 mm long from the coated electricwire produced by the above mentioned procedure,

placing the test piece on a table at a room temperature of 25° C.,

reciprocating a blade on the surface of coating material of the testpiece along the axial direction thereof in a range of 10 mm long with aload of 7 N at a rate of 50 times per minute, and

counting the reciprocation number until the coating layer was abradedand the blade become in contact with the conductor.

Thereafter, the test piece was shifted in 100 mm and rotated at 90degree in a clockwise direction to be subject to the next measurementwith the same manner. This measurement was conducted totally three timesfor the same test piece. When the minimum reciprocation number is 200 ormore, the test piece was considered as acceptable quality level.

(Evaluation of Insulating Strength)

Evaluation was carried out as follows:

cutting out the test piece with 900 mm long from the coated electricwire produced by the above mentioned procedure,

peeling off the insulating bodies with 25 mm long respectively atopposite ends of the test piece,

stretching the test piece straightly without providing a tension, and

then putting it on an iron bar with φ 3.2 mm to cross them at rightangle.

Thereafter, the test piece was loaded with an iron anvil of which weightwas increased at a rate of 22.2 N (2.27 kgf) per minute with alever-advantage 10. The load was measured, when the iron bar become incontact with the conductor.

After having measured at one point, the test piece was shifted in 50 mmand rotated at 90 degree in a clockwise direction to be subjected to thenext measurement. In this manner, totally 4 points were measured for thesame test piece. This measurement was repeated three times (n=3) andthen calculating average load. The test piece having average load of 20N or more was considered as acceptable quality level.

(Evaluation of Flame Retardance)

The evaluation was conducted according to the standard of JASO D611-94defined by Society of Automotive Engineers of Japan, Inc. A test piecewas cut out with 300 mm long from the coated electric wire produced bythe above mentioned procedure. Thereafter, the test piece was put in abox made of iron and placed horizontally;

preparing a Bunsen burner with a diameter of 10 mm to form a reducingflame, putting a tip of the reducing flame at a lower and center side ofthe test piece until the test piece threw out its own flame in 30seconds, and then carefully taking away the flame of the burner tomeasure a time remaining the flame of the test piece. The test piecehaving a flame-remaining time of 15 seconds or less was considered asacceptable quality level, and that of more than 15 seconds wasconsidered as not acceptable.

(Evaluation of Flexibility)

Flexibility was judged from the hand feeling obtained when bending awire by hands; the wire giving favorable feeling was considered asacceptable quality level, and that giving unfavorable feeling wasconsidered as not acceptable.

The results obtained are shown in Tables 1 to 4. In Tables, evaluationresults of insulating strength, flame retardance, and flexibility areexhibited with a mark of ◯ for the acceptable quality levels and a markof X for the unacceptable quality levels.

The materials shown in the following Tables were the materialsrepresented as follows:

-   PP1 (Polypropylene): Idemitu Petrochemical Co., Ltd., E-150GK,-   PP2 (Polypropylene): SHIRAISHI CALCIUM Co., Ltd., Polybond 3002,-   HDPE (High-density polyethylene): Japan Polypropylene Corporation,    Novatech HY540,-   LLDPE (Linear low-density polyethylene): Japan Polypropylene    Corporation, Novatech UE320,-   EVA (Ethylene-vinylacetate): DU PONT-MITSUI POLYCHEMICALS Co., Ltd.,    Evaflex EV270,-   SEBS (Styrene-ethylene-butylene-styrene): KRATON POLYMERS JAPAN Co.,    Ltd., KRATON FG1901X,-   Magnesium hydroxide 1: Martinswerk GmbH MAGNIFIN H10,-   Magnesium hydroxide 2: Kyowa Chemical Industry Co., Ltd., Kisma 5J,-   Basic magnesium sulfate: Ube Material Industries Ltd., Mos Hige,-   Antiaging agent: Ciba Specialty Chemicals K.K., IRGANOX1010,-   Metal deactivator: Ciba Specialty Chemicals K.K., IRGANOX1024,-   Sulfur-based additive: OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD.,    Nocrack MB,-   Metal oxide: HakusuiTech Co., Ltd., zinc oxide

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 11Example 12 Outer Inner Outer Inner Outer Inner Outer Inner Outer Innerlayer layer layer layer layer layer layer layer layer layer ProducingConditions P P 1 100 50 100 90 100 90 80 60 P P 2 10 20 10 H D P E 90 70L L D P E 50 E V A 30 30 S E B S 10 10 Magnesium 60 120 hydroxide 1Magnesium 140 200 160 hydroxide 2 Basic magnesium sulfate Antiaging 1 33 3 1 1 1 1 agent Metal 1 1 1 0.5 0.5 3 1 deactivator Sulfur-based 5 5 53 additive Metal oxide 5 5 5 3 Evaluation Results Thickness of Outer 550 40 100 70 Layer (μm) Hardness of Outer D 60 D 61 D 60 D 52 D 62Material Abrasion 500 2500 2100 1000 3500 resistance Insulating ◯ ◯ ◯ ◯◯ strength Flame ◯ ◯ ◯ ◯ ◯ retardance Flexibility ◯ ◯ ◯ ◯ ◯

TABLE 2 Comparative Example 13 Example 7 Example 8 Example 9 Example 10Outer Inner Outer Inner Outer Inner Outer Inner Outer Inner layer layerlayer layer layer layer layer layer layer layer Producing Conditions P P1 90 90 100 80 P P 2 10 10 H D P E 100 50 100 50 100 L L D P E 50 60 E VA 30 S E B S 20 40 20 Magnesium 50 100 90 hydroxide 1 Magnesium 140 120hydroxide 2 Basic 30 10 20 magnesium sulfate Antiaging 1 1 2 3 1 1 agentMetal 1 2 0.2 0.5 0.5 1 deactivator Sulfur-based 3 5 5 additive Metaloxide 5 5 5 Evaluation Results Thickness of Outer 20 5 40 35 50 Layer(μm) Hardness of Outer D 57 D 66 D 56 D 56 D 60 Material Abrasion 6001150 1400 1000 2200 resistance Insulating ◯ ◯ ◯ ◯ ◯ strength Flame ◯ ◯ ◯◯ ◯ retardance Flexibility ◯ ◯ ◯ ◯ ◯

TABLE 3 Comparative Comparative Comparative Comparative Comparativeexample 1 example 2 example 3 example 4 example 5 Outer Inner OuterInner Outer Inner Outer Inner Outer Inner layer layer layer layer layerlayer layer layer layer layer Producing Conditions P P 1 100 90 90 90 PP 2 10 10 H D P E 90 100 50 100 50 L L D P E 100 50 50 E V A 10 S E B S10 Magnesium 140 40 100 hydroxide 1 Magnesium 40 140 230 hydroxide 2Basic 10 magnesium sulfate Antiaging 2 1 3 1 1 0.5 1 agent Metal 0.5 1 33 1 deactivator Sulfur-based 3 3 additive Metal oxide 3 3 EvaluationResults Thickness of Outer 60 40 30 30 4 Layer μm) Hardness of Outer D40≧ D 62 D 56 D 56 D 65 Material Abrasion 150 2400 700 500 1100resistance Insulating X X ◯ ◯ X strength Flame ◯ ◯ X ◯ ◯ retardanceFlexibility ◯ X ◯ X ◯

TABLE 4 Comparative Comparative Comparative Comparative Comparativeexample 6 example 7 example 8 example 9 example 10 Outer Inner OuterInner Outer Inner Outer Inner One layer layer layer layer layer layerlayer layer layer Producing Conditions P P 1 90 90 100 60 P P 2 10 10 10H D P E 100 80 100 80 50 L L D P E 50 E V A 30 20 20 S E B S Magnesium100 40 120 50 hydroxide 1 Magnesium 50 hydroxide 2 Basic 10 10 magnesiumsulfate Antiaging 0.5 1 1 1 1 1 agent Metal 1 1 1 1 1 deactivatorSulfur-based 5 additive Metal oxide 5 Evaluation Results Thickness ofOuter 110 10 30 80 — Layer (μm) Hardness of Outer D 65 D 60 D 57 D 56 —Material Abrasion 4000 850 900 850 100 resistance Insulating ◯ ◯ ◯ ◯ Xstrength Flame X X X X ◯ retardance Flexibility X ◯ ◯ ◯ ◯

As apparent from Examples 1-10, the coated electric wires of theinvention exhibit sufficient Abrasion resistance, Insulating strength,Flame retardance and Flexibility. On the other hand, the coated electricwires of Comparative examples 1 and 10 are not good in Abrasionresistance and Insulating strength. The coated electric wires of theother Comparative examples are not satisfactory in at least one propertyof Insulating strength, Flame retardance and Flexibility, either.

1. A coated electric wire comprising a conductor and a coating layercovering the outer circumference of the conductor, wherein the coatinglayer has an outer layer comprising a halogen-free resin compositionwith a Shore D hardness of 50 or more and an inner layer comprising anolefin based flame retardant resin composition, the coating layer has atotal thickness of 0.3 mm or less, the outer layer mentioned abovecontains oxide fillers, silicate fillers, antiaging agents, lubricants,plasticizers, or antistatic agents in an amount of 30 parts by weight orless with respect to 100 parts by weight of the base polymer of theouter layer mentioned above, the layer thickness of the outer layermentioned above is 5 to 50 μm, the inner layer mentioned above containsa metal hydrate in an amount of 60 to 140 parts by weight with respectto 100 parts by weight of a base polymer of the inner layer mentionedabove, and, when letting X (μm) be the layer thickness of the outerlayer mentioned above and Y(phr) be the amount of a flame retardant tobe added to the inner layer mentioned above, the formula Y−40≧1.2X issatisfied.
 2. The coated electric wire according to claim 1, wherein thehalogen-free resin composition mentioned above is an olefinic resincomposition.